Tremors of the type considered herein are unintentional muscle movements in the human body. Both healthy individuals and people diagnosed with neurologically caused disorders suffer from tremors. Essential tremor is a common tremor type and as many as ten million people in the U.S. alone suffer from this type of tremor. It is especially common among people 65 years old and older and can be found in as many as 50% of this age group. The effects of essential tremor can cause significant disability. People diagnosed with this tremor can have trouble performing necessary functions, such as eating and drinking Tremor also interferes with daily activities such as using keys, typing on a computer, or applying make-up, causing a reduction in the quality of life for those people. Additionally, individuals affected by tremor who work in occupations requiring fine muscle control (e.g. artists, surgeons, musicians, drafters) are often forced to retire as a result.
Various treatments for essential tremor exist, but they have shown limited effectiveness. For example, pharmacologic treatments are known to help alleviate unwanted muscle motion. However, the effectiveness of these treatments can vary and they are typically prescribed on a trial-and-error basis. Additionally, side effects can be significant because the beta blockers commonly used for essential tremor mask signs of hypoglycemia and may cause memory loss and confusion in the elderly. For patients who are resistant to drug treatment or have severely disabling tremor, pharmacologic solutions alone are often inadequate. In these cases surgical treatments such as thalamotomy and thalamic deep brain stimulation may be used. But these treatments involve operative and post-operative risks and are not always desirable.
Despite current treatment options, many patients possess tremor that is not curable or they may decline treatment because they consider the risks and side-effects to be too great. One approach for this group is the use of tremor suppression devices that physically force a person's tremor to cease. These devices are supported by a large unmoving (grounded) mass and deliver an appropriately timed and measured force against the user's affected body part. For instance, physically grounded joysticks supported by a heavy table have been developed to mechanically dampen a person's tremor to aid in the overall control of electronic wheelchairs. In another example, wearable prosthetics suppress tremor using actively controlled forces that are produced from the bulk of the operator's body. While physically grounded devices are capable of forcing a person's tremor to cease, they suffer from some disadvantages. One significant disadvantage is user discomfort or pain that occurs when relatively large forces are applied to an affected limb. Another problem is that these devices typically do not distinguish between intended and unintended motions. Therefore, patients encounter resistance to all regular directed movements making the experience of wearing the device awkward and obtrusive. Additionally, most grounded prosthetics require a complex structure, adding to overall size, weight, and cost, which can render them impractical for use in daily activities.
In fields unrelated to tremor management and treatment, the use of active stabilizing handgrips is known for rifles and other devices involving azimuth and elevation control of a person's aim. See, for example, U.S. Patent Application Publication No. 2006/0194173 which discloses various embodiments of a handgrip that uses shape memory alloy (SMA) wires to effect elevation and azimuth stabilization.